This invention is generally related to a system for protecting and controlling substation main-circuit components, and more particularly to a system including AC electric value sensors, analogue-to-digital converters and communication means for protecting and controlling substation main-circuit components.
Now an example of prior-art system for protecting and controlling substation main-circuit components in a substation is discussed referring to FIG. 53. The system has digital operational processors and communication means. The substation has a main control building 1 which contains substation controlling-and-monitoring equipment 4 including a remote controlling-and-monitoring equipment 2 for interfacing information to and from a remote control station (not shown), and a collective controlling-and-monitoring equipment 3 for controlling and monitoring the whole substation. The main control building 1 also contains main-circuit controllers (bay control units) 5-1 through 5-n, each corresponding to a main circuit such as a transmission line.
The remote controlling-and-monitoring unit 2, the collective controlling-and-monitoring equipment 3 and the main-circuit controllers 5-1 through 5-n are connected to each other via a station bus 7. The main control building 1 further contains protecting units 6-1 through 6-n which are connected to their respective main-circuit controllers 5-1 through 5-n via cables 17. The protecting units 6-1 through 6-n protect their respective substation main-circuit components 8-1 through 8-n as described below in detail.
The substation main-circuit components 8-1 through 8-n are connected to the main-circuit controllers 5-1 through 5-n and the protecting units 6-1 through 6-n via corresponding local controllers 9-1 through 9-n. The substation main-circuit component 8-1 includes a current transformer 10, a voltage transformer 11, a switchgear 12 such as circuit breaker or a disconnecting switch, a bus line 13 and a transmission line 14. The current transformer 10, the voltage transformer 11, the switchgear 12 and the local controller 9-1 are of analogue type. Thus, numbers of cables 15 and 16 corresponding to the volume of the information transmitted are used for the connection between the substation main-circuit component 8-1 and the main-circuit controller 5-1, and for the connection between the local controller 9-1 and the main-circuit controller 5-1 or the protecting unit 6-1.
The remote controlling-and-monitoring unit 2, the collective controlling-and-monitoring unit 3, the main-circuit controllers 5-1 through 5-n and the protecting units 6-1 through 6-n are of digital type using digital operation processors. The station bus 7 is used for information transmission between those units and controllers, except for the connections between the main-circuit controllers 5-1 through 5-n and the corresponding protecting units 6-1 through 6-n, where electric cables 17 are typically used as connection media corresponding to the volume of the information transmitted since interfaces with contact positions are typically used.
FIG. 54 shows a conventional hardware structure of one of the main-circuit controllers 5-1 through 5-n, collectively denoted as reference “5”. The main-circuit controller 5 has an input converting unit 501 for inputting an AC electric value such as an electric current or a voltage, for filtering the analogue input and for transforming to a level of electric current or voltage to be directly treated by an electric circuit for analogue-to-digital conversion. The main-circuit controller 5 also has an input unit (DI) 502 loaded with a contact input circuit, and an output unit (DO) 503 loaded with a contact output circuit. The main-circuit controller 5 also has an analogue input unit (AI) 504 for processing the AC current value including analogue-to-digital conversion, a processing unit (CPU) 505 for processing for protecting, a transmission unit 506 for processing for transmission, and an electric power supply 507.
Each of the protecting units 6-1 through 6-n, similarly to the main-circuit controller 5, has an input converting unit (not shown) for inputting an AC electric value such as an electric current or a voltage, for filtering the analogue input and for transforming to a level of electric current or voltage to be directly treated by an electric circuit for analogue-to-digital conversion. The protecting unit also has an input unit (DI) loaded with a contact input circuit, and an output unit (DO) loaded with a contact output circuit. The protecting unit also has an analogue input unit (AI) for processing the AC current value including analogue-to-digital conversion, a processing unit (CPU) for processing for controlling, a transmission unit for processing for transmission, and an electric power supply.
The input units and the output units can be loaded with required numbers of units corresponding to the numbers of inputs and outputs. Thus, typically, major parts of the main-circuit controllers 5-1 through 5-n and the protecting units 6-1 through 6-n are occupied by the input units and the output units.
The protecting and controlling units in the art have been partly digitized. Thus, the units have become more compact and less expensive. Furthermore, the units requires less manpower for maintenance due to loaded self-diagnostic function, and reduction of electric cables has been achieved by applying communication means for transmitting information between the units.
However, there are following problems left to be solved because analogue techniques are still used in the circuits for driving the substation main-circuit components and in the electric current and voltage transformer circuits:
(1) Electric cables and analogue information have been used in the substation main-circuit components and in the information transmission between the protecting-and-controlling units for protecting and controlling the substation main-circuit components. Therefore, the protecting-and-controlling units require as input and output circuits, contact input circuits and contact output circuits which can accommodate higher voltage and larger current compared to digital circuits. In addition, all the protecting-and-controlling units require input conversion units for transforming the currents and voltages into certain easily-handled levels, and analogue input circuits for converting the analogue values to digital values. Those requirements resulted in the protecting-and-controlling units of relatively large size and less cost-effectiveness.
(2) Although processing parts for protecting and controlling in the protecting-and-controlling units have become more compact due to the digitalization, the volumes of the hardware constituting the input and output circuits are still larger for isolation from the substation main-circuit components due to the cause described in (1) above, and large space is required for large volume of electric cables. Therefore, each one of the protecting unit and controlling unit for each main circuit must be contained in a separate chassis and must be independent, which has resulted in wider space required for installation.
(3) Since parallel connections for analogue information have been used between the main-circuit components and the protecting-and-controlling units, large volume of cables are required corresponding to the number of signals transmitted. Thus, cost of cables, of construction for cable pits and of cable installation have been enhanced, resulting in higher cost of the substation construction.
(4) Since the driving circuits for the substation main-circuit components and the transformer circuits for current and voltage measurement have had analogue technique, hardware sizes have been large, which has caused the sizes of the substation main-circuit components larger. Besides, work for assembling and connecting the circuits in the manufacturing factories and on the substation construction sites have required large manpower.
(5) Because of the reasons similar to those described in (4) above, real-time monitoring and automatic diagnosis of the substation main-circuit components have been difficult, which have resulted in insufficient information about the maintenance, and which have been an obstacle for manpower reduction.
(6) Since all the circuits and components have not been digitized and all the devices have not been connected by communication means, the volume of the information has been limited and it has been difficult to add new functions. In addition, optimum system construction has been difficult utilizing the data each component has.